The extracellular matrix proteins of the bones and teeth are key elements in the structure and metabolism of these tissues. The goal of this project is to study matrix proteins specific to each mineralizing skeletal tissue in order to understand their molecular structure and biological function. Analytical procedures (polyacrylamide gel electrophoresis, immunoblotting, specific dye-binding, RIA, ELISA, etc.) have been developed to quantitate the levels of bone specific noncollagenous proteins and a novel short chain collagen in (a) surgical specimens of bony tissue (osteonectin, bone sialoproteins I and II, bone proteoglycans I and II, and the short chain collagen, and (b) serum (osteonectin). Changes in the noncollagenous protein profile with age and variety of bone (and tooth) diseases have been observed in man and several animal models. Recent developments in monoclonal antibody production against osteonectin suggest that a family of related proteins similar to bone osteonectin may exist in soft tissues and in tissue culture.